Due to the friction when the rocket re-enters atmosphere .the hotness comes because the work is done again frictional force
This does not happen on model rockets,of course.
From the rocket's movement energy (formally called kinetic energy). As the rocket slows down through friction, its kinetic energy is converted mainly to heat energy.
The energy that heats the rocket comes from gravity, but is released in heat as the nose cone encounters friction from air molecules. While in space, there are few molecules to encounter, but as it enters the thicker atmosphere, collisions increase and this produces heat in the air and on the rocket nose. In the case of the Space Shuttle, all of its initial velocity (energy) gained at launch is expended as heat as the shuttle lands, and it returns to its original gravitational state again.
You use fins and a nose cone on a bottle rocket because the cone reduces the drag on the rocket, and the fins help stabilize the rocket.
no
typically the nose cone is filled with a parachute to the rocket arrives on the ground safely.
an
fin and tip (cone).
It streamlines the rocket and allows more speed.
A cone on top of a cylinder.
"Rocket nose cone" pretty much says it all, I really don't think there is another suitable name.
A perfect cone
It streamlines the nose, so the rocket flies faster.